American Chestnut

[046]

how sad!!!

so a 14in DBH chestnut is considered good sized?

 

[moray]

Nowadays, yes, 14 in. is good-sized. The best tree in Maine is 34 in. DBH. In the old days the trees lasted a lot longer and obviously got a whole lot bigger.

Have you found the pollinator for your big tree yet?

 

[S Mc]

Have you found the pollinator for your big tree yet?

The American chestnut is monoecious and therefore, capable of "self-pollination". In Harlow & Harrar's Textbook of Dendrology, 9th Ed, it is stated that the tree is anemophilous (wind-pollinated) and entomophilous (insect-pollinated) or a combination of both. However, Johnson (1988) found that the American species of Castanea are primarily wind pollinated.

So I am construing from your questioning the existance of a pollinator close by that the incidence of viable pollination increases with multiple trees. Is this correct? (I realize many wind-pollinated species do perform better with multiple pollinators.)

In the breeding orchards you have mentioned, do they take cuttings into a controlled green house for the innoculation? How is that controlled?

Moray, thanks for so much interesting information! Actually to all the informational posts on this subject. Really fascinating. The points raised about the time span necessary to see results is one of the stumbling blocks to tree management. Everyone wants immediate results and trees just simply have a different prospective on what that means. It takes dedication and commitment on a multi-generational basis to pursue answers...and all too often lead us to more questions.

Sylvia

 

[046]

hmmmm... more new info..

have always thought american chestnut required a second tree to pollinate. just assumed there was a second chestnut tree closeby.

fertile nuts to stunted nuts ratio for the mature Tulsa tree is on the order of 20 to 1.

it survived a nasty ice storm much better than surrounding oaks. seems fruit trees in general are designed to carry much larger loads without breaking. most of the pears and apple trees survived the Tulsa ice storm without major damage.

 

[moray]

The American chestnut is monoecious and therefore, capable of "self-pollination"...
So I am construing from your questioning the existance of a pollinator close by that the incidence of viable pollination increases with multiple trees...

In the breeding orchards you have mentioned, do they take cuttings into a controlled green house for the innoculation? How is that controlled?...

Sylvia, you are right that the chestnut is monoecious. The male flowers make a spectacular display that can be seen half a mile away. But the tree is not self-fertile (maybe rarely so). There are lone trees in my area that flower profusely every year and litter the ground with burrs in the fall, but all the burrs are full of duds. The dying tree was near several others (50 feet to 200 feet)--they supplied the necessary pollen, and 80 or 90% of the nuts were fertile, the rest being duds.

Pollination in the breeding program is accomplished in two stages. The operator uses some sort of bucket lift to get up into the target tree, then strips a likely branch of all male catkins (which greatly outnumber the female flowers), leaving only the female flowers. Bags are placed over the female flowers, usually 100 per tree and 2 or 3 per branch. A few days to a week later, the crew returns with a vial of pollen from the desired genetic source and individually removes the bags, applies pollen, and reinstalls the bags. A few bags are left on unpollinated flowers as controls.

In the fall the bags are removed and the burrs collected. If the control bags contain any fertile nuts, the whole experiment is deemed to have been contaminated with local pollen before bagging began, and the harvested nuts will likely end up in a tasty soup. The people in the Maine program have a keen eye for the timing--they seem to know almost to the hour when to bag to avoid local pollen, and when to pollinate before the female flowers lose viability. It's a great project.

 

[eljefe]

seeds or seedlings

Hi, I would very much like to obtain either seeds or seedlings. I would plant on an island which might help keep the blight away. Island is protected and will never be developed. It would be great to see these trees come back to forests. Eljefe

 

[S Mc]

Moray, I'm trying to understand this. If the tree is monoecious, then it has male and female flowers. Why isn't it self-fertile? Is the prevailing wind in this area constant enough or severe enough to preclude the pollen staying within the vicinity of the host tree? Otherwise, it should self-pollinate, shouldn't it? If they are self-incompatible, I am curious as to why the dendrology books seem to leave this fact out. Is this a new circumstance due to the blight? Or has this just become evident with the decimation of the vast chestnut forests bringing the necessity of a pollinator in the vicinity to light?

Thank you for the breeding information on the trees. It really is a fascinating and awesome undertaking.

I was also wondering, though, about the innoculation of the blight fungal pathogen to determine resistance. You said that this breeding orchard innoculated trees in an effort to determine resistance. How is this controlled?

Sylvia

 

[S Mc]

046, your mission should you choose to accept it...

Find out if you have a pollinator in the vicinity of your Tulsa chestnut. (Start walking upwind, using Ninja squirrel techniques...should be no problem.) opcorn:

I find this fascinating. Because if it is a lone tree AND producing viable nuts AND has stayed healthy, what conclusions might be drawn from this?

Sylvia

 

[Musclenut]

I work for a telephone company and due to the state widening a hwy. I was able to bring home several American Chestnut telephone poles that were suposably in the ground since the 30's and 40's. They still looked almost new. Some day they'll make me a nice fence. Telephone poles in general are hard on a chainsaw but old chestnut poles are real bad.

 

[appalachianarbo]

Bags are placed over the female flowers, usually 100 per tree and 2 or 3 per branch. A few days to a week later, the crew returns with a vial of pollen from the desired genetic source and individually removes the bags, applies pollen, and reinstalls the bags. A few bags are left on unpollinated flowers as controls.

In the fall the bags are removed and the burrs collected.

I've done this for the ACF. I climbed the trees though - No lift for me. The biggest was 16" DBH.

My father in law has a hybrid that's about 15' tall now. It's from the Biltmore Estate's planting (from 2003 or 2004 or so?)

 

[moray]

Moray, I'm trying to understand this. If the tree is monoecious, then it has male and female flowers. Why isn't it self-fertile?...

I was also wondering, though, about the innoculation of the blight fungal pathogen to determine resistance. You said that this breeding orchard innoculated trees in an effort to determine resistance. How is this controlled?

Good questions. I suppose there are two answers to the self-fertile question, one mechanical and the other evolutionary. The evolutionary answer is pretty straightforward: one of the major purported benefits of sexual reproduction--genetic diversity of offspring--is somewhat diminished if a plant pollinates itself. One could speculate that dioecious plants came about because plants with only one flower type absolutely could not pollinate themselves. It is worth noting that, by analogy, animals are almost without exception "dioecious".

I wish I had a list of examples right at hand to illustrate the point, but I believe it is actually quite common that a plant goes to some pains to avoid self pollination. Even in plants with perfect flowers there are often barriers to self pollination. Orchids, for example, represent a huge group whose flowers have a shape that makes self pollination very difficult. The mechanical and chemical means to prevent self pollination could include timing pollen release before the stigmas are ready to receive pollen, chemical markers on the pollen that the stigmas recognize as "self", and so on. Suffice it to say, in the case of American chestnut self pollination is very rare.

To challenge hybrid orchard plants with the blight, a small hole is drilled a half inch or so into the trunk of each tree a couple of feet above the ground. Fungal innoculum is smeared into the hole, and the hole is plugged. A few months later (there is an exact protocol for all this, but I don't know the details) all the challenged trees are inspected and rated from 1 to 5 according to severity of the resulting blight canker. Only the trees with the smallest cankers are kept for breeding the next year. Apparently they will survive long enough to produce pollen, or maybe even nuts, and so the chain remains unbroken. As far as I am aware, the blight is lethal to all hybrids because, at best, they can have only half the Chinese resistance genes.

The pictures below show part of an orchard of 9-yr-old trees, a closer view of a tree showing its size (about 5 inches in diameter), and a closeup showing a sunken blight canker a couple of days after inspection. The arrow points to the site of innoculation. I believe that it was a relatively large canker, indicating the tree had very little resistance and was a candidate to be culled.

 

[moray]

Hi, I would very much like to obtain either seeds or seedlings. I would plant on an island which might help keep the blight away. Island is protected and will never be developed. It would be great to see these trees come back to forests. Eljefe

Google TACF. Then find your state chapter, or else find the Virginia chapter. One of those should be happy to sell you some seeds or seedlings. Virginia has the biggest and most advanced recovery program.